Pebble heater apparatus



1 1957 D. s. HALL 2,797,335

PEBBLE HEATER APPARATUS Filed Dec. 28, 1953 2 sheets-sheet 1 as 3 l 43 1v v 46 H 42 44 24.

INVENTOR. 3| D.S.HALL

F/G. BY

ATTQRNEYEE D. S. HALL PEBBLE HEATER APPARATUS June 25, 1957 2Sheets-Sheet 2 Filed Dec. 28, 1955 INVENTOR. D. s. H ALL Wag ATTORNEYSUnite States Patent PEBBLE HEATER APPARATUS Dick S. Hall, Phillips,Tex., assignor to Phillips Petroleum Company, a corporation of DelawareApplication December 28, 1953, Serial No. 400,462 6 Claims. c1. ass-223This invention relates to pebble heater apparatus. In a more specificaspect, it relates to a means for measuring the pebble circulation ratein a pebble heater apparatus. In another of its more specific aspects,it relates to a method for measuring the pebble circulation rate in ,apebble heater apparatus.

In carrying out thermal conversion processes in pebble heater apparatus,a flowing mass of solid heat exchange material, heated to a hightemperature by passing gas therethrough in a first direct heat exchangestep, is thereafter caused to contact gaseous reactant materials in asecond direct heat exchange. The conventional pebble heater apparatusgenerally comprises two chambers which may be disposed in substantiallyvertical alignment. The solid heat exchange material is introduced intothe upper portion of the first or upper chamber where the material formsa moving bed of solid heat exchange material which flows downwardlythrough the chamber in direct heat exchange with hot gaseous heatexchange material. In the heat exchange, the solid heat exchangematerial is heated to a high temperature and then passed to a second .orlower chamber in which the hot solid heat exchange material is caused tocontact gaseous reactant materials in a second direct heat exchangerelation furnishing heat for the treatment or conversion of the gaseousmaterials.

The solid heat exchange material, cooled as a result of the second heatexchange, emerges from the bottom of the second chamber and flowsdownwardly to the lower part of an elevator which elevates the materialto the upper end of a conduit leading into the upper portion of thefirst chamber.

Solid heat exchange material which is conventionally used in pebbleheater apparatus is generally called pebbles. For a more completedescription of the pebbles which can be utilized, reference may be had tU .8. Patent No. 2,536,436.

The pebbles are heated in the upper chamber to a temperature generallyin the range of 1400 F. to 3200" F.

Ordinarily, pebble inlet temperatures in the lower chamber are about 100F. to 500 F. below the average combustion gas temperature within theupper chamber. In processes for the production of ethylene from lighthydrocarbons such as ethane or propane, the pebble temperatures in thelower reaction chamber are usually in the range of 1200 F. to 1800" F.In the production of acetylene by pyrolysis of hydrocarbons,temperatures in the range of 1800 F. to 3000 F. are desirable. In thepractice of such processes, the cracking reaction involved isendothermic requiring for a particular hydrocarbon feed a specificamount of heat to effect the desired depth of cracking. The heatrequired for this reaction is delivered by the pebbles in the secondheat exchange relation previously referred to. Itv should be apparentthat in any given process the rate of flow of pebbles through the lowerchamber as well as the temperature of the pebbles is determinative ofthe amount of heat available for the cracking reaction and the amount ofhydrocarbon 2,797,335 Patented June 25, 1957 feed which should beintroduced into the reaction chamber. Furthermore, the temperature towhich the pebbles are heated in the upper chamber is related to theresidence time therein during which the pebbles undergo a first heatexchange with hot combustion gases. In order to operate a pebble heaterapparatus so as to obtain the most efiicient cracking of the hydrocarbonfeed, it becomes important to be able to measure expeditiously thecirculation rate of the pebbles through the system.

The following objects will be attained by the various aspects of theinvention.

It is an object of the present invention to provide a means formeasuring the pebble circulation rate in pebble heater apparatus.

Another object is to provide a method for measuring the pebblecirculation rate in pebble heater apparatus.

A further object is to provide a means and method whereby the pebblecirculation rate in a pebble heater system can be automaticallydetermined.

Various other objects, advantages and features of the invention willbecome apparent from the accompanying disclosure.

In accordance with this invention, in a pebble heater system comprisinga pebble heater chamber positioned above a pebble reaction chamber, thelower end of the pebble reaction chamber being connected to the upperend of the pebble heater chamber by a pebble elevating means, a pebblemeasuring pot is disposed above the pebble heater chamber. The pebblemeasuring pot is provided with a pebble inlet conduit which is connectedto the pebble conduit extending between the upper end of the pebbleelevating means and the pebble inlet of the pebble heater chamber. Flowcontrol means are provided whereby the flow of pebbles into the upperend of the pebble heater chamber from the pebble elevating means can bediverted into the pebble measuring pot. By measuring the time intervalrequired to fill the pebble measuring pot of known volume, the pebblecirculation rate of the pebble heater system can be readily determined.In a preferred embodiment of the invention, means are provided wherebythe pebble circulation rate can be automatically determined. The lowerend of the measuring pot is provided with a pebble outlet connected tothe upper end portion of the pebble heater chamber, thereby providingmeans for passing the pebbles into the upper portion of the reactionchamber. By operating in this manner, it is possible at any time duringthe progress of the particular process being carried on in thepebbleheater system to determine the pebble circulation rate through thatsystem.

A more complete understanding of the invention may be obtained byreference to the following description and the drawing in which:

Figure 1 is a diagrammatic elevation of the apparatus of the invention,and

Figure 2 is an elevation illustrating a preferred embodiment of theinvention.

Referring now to the drawing and in particular to Figure 1, the pebbleheater apparatus comprises an upright elongated shell 10 closed at itsupper and lower ends by closure members 11 and 12, respectively. Gaseousetlluent outlet conduit 13 extends from the upper portion of the pebbleheater chamber formed within shell 10 while heating material inlet means14 is provided in the lower portion of that chamber. Upright elongatedshell 16, closed at its upper and lower ends by closure members 17 and18, respectively, is disposed below shell 10. Pebble conduit means suchas conduit 19 or a plurality of such conduits, extending between closuremember 12 of shell 10 and closure member 17 of shell 16, connects thepebble heater chamber with the reactor chamber formed within shell 16.Gaseous eifluent outlet conduit 'tion of elevator 24. Pebble feeder 26is provided intermediate the ends of pebble outlet conduit 23 and may bea conventional pebble feeder such as a star valve, a gate valve, arotatable table feeder, or the like. It is also within the scope of theinvention to omit pebble feeder 26 and provide for the control of pebbleflow by means associated with elevator 24 as disclosed in the copendingapplication of Lloyd E. Dean, Serial No. 309,252, filed September 12,1952, now abandoned.

Elevator 24, which is illustrated as being of the gas lift type,comprises engaging pot 27, gas lift conduit 28, and disengaging chamber29. Lift gas inlet conduit 31 is connected to the lower end of engagingpot 27 while gaseous efiluent conduit 32 is provided in the upper endportion of disengaging chamber 29. It is also within the contemplationof the invention to utilize other pebble elevating means such as abucket type elevator to raise the pebbles from the pebble reactionchamber to the pebble heater chamber.

Pebble conduit 33 containing a flow control means such as gate valve 34extends from separator chamber 29 to pebble inlet 35. A measuring potcomprising container 36 is disposed above shell 10. As illustrated,container 36 is supported upon closure member 11 of shell by means ofupright support members 37. It is within the scope of the invention,however, to provide other means for supporting container 36 above thepebble heater chamber. Pebble inlet conduit 38 extends between pebbleconduit 33 and the upper end portion of container 36. As illustrated,conduit 38 is divided into two parts, the upper part containing a flowcontrol means such as a gate or plug valve 39 while the upper end 40 ofthe lower part is flared. By constructing the pebble inlet conduit inthis manner, pebble flow into the measuring pot can be observed and avisual determination made of the time required to fill measuring pot 36with pebbles. Pebble outlet conduit 41 containing a flow control means42 extends between the substantially conical bottom closure member 43 ofcontainer 36 and closure member 11 of shell 10. A second pebble outlet44 containing a flow control means 46 is also connected to bottomclosure member 43 of container 36. Conduit 44 provides means forremoving pebbles from container 36 which it is not desired to return tothe pebble heater chamber and can lead to pebble storage facilities ormeans for weighing pebbles.

Referring to Figure 2, which illustrates a preferred embodiment of theinvention, a first source of light 51 is provided in the upper side ofpebble measuring pot 36. A first photoelectric cell 52 .is positionedopposite source of light 51 and in the direct rays of a beam thrown bythat source. Source of light 51 and photoelectric cell 52 are disposed asubstantial distance to one side of the vertical axis of the pebblemeasuring pot so that the pebble stream flowing from inlet conduit 38will not interrupt the beam of light. A second source of light 53 and asecond photoelectric cell 54 are similarly positioned in the lowerportion of the pebble measuring pot. Photoelectric cells 52 and 54 areoperatively connected to a timer-controller 56 which is adapted to startcounting time when the light beam between light source 53 andphotoelectric cell 54 is broken and to stop counting time when the lightbeam between light source 51 and photoelectric cell 52 is broken. Thetimer can be graduated so as to indicate directly pebble circulationrate in thousands of pounds per hour or other suitable rate. Thetimer-controller is also operatively connected to valves'34 and 39, andfunctions to open valve 34 and to close valve 39 when the light beambetween light source 51 and photoelectric cell '52 is interrupted.

In the operation of the pebble heater apparatus of Figure 1, pebblesareheated in the pebble heater chamber formed within shell 10 by contactwith hot gaseous heat exchange material which may result from thecombustion of fuel outside of the heater chamber or in the lower portionof that chamber in a combustion zone separated from the pebble mass, orby burning a fuel in direct contact with the pebble mass within thechamber. Pebbles are introduced into the pebble heater chamber throughpebble inlet 35 and form a contiguous gravilating mass which extendsdownwardly through shell 10, pebble conduit 19, shell 16, and pebbleoutlet conduit 23 to feeder 26. The pebbles are heated in the pebbleheater chamber to a temperature generally in the approximate range of1400 F. to 3200 F., and thereafter the hot pebbles are gravitatedthrough conduit 19 into the upper portion of the reaction chamber formedwithin shell 16. Usually pebble inlet temperatures in the reactor areabout F. to 500 F. below the average combustion gas temperature withinthe pebble heater chamber. Gaseous reactant materials introduced intothe reaction chamber through inlet conduit 22 contact the gravitatingmass of hot pebbles and undergo reaction. The product containing gas iswithdrawn through gaseous eflluent outlet conduit 21 and thereafterpassed to quenching means and a purification system, not shown.

The cooled pebbles flow from the bottom of the reaction chamber throughpebble outlet conduit 23 and pass therethrough into engaging pot 27 at arate dependent upon the operation of the pebble feeder means employed.In the engaging pot, the pebbles contact a stream of lift gas, such asair, which is introduced into the lower end of the engaging pot throughlift gas inlet conduit 31. Air is furnished under a pressure and at arate of flow suflicient to lift the .pebblcs from the engaging pot tothe top of elevator 24. Prior to entry into elevator 24, the air can bepassed through a heater in order to raise the air temperature to theapproximate temperature of the pebbles, thereby preventing thermalshock. The pebbles are .raised by the air stream through gas liftconduit 28 to .the'top of the elevator where the pebbles fall out of the.air stream in disengaging chamber 29 and pass down pebble conduit 33toward the top of the pebble heater chamber. The air is withdrawn fromthe separator chamber through gaseous efliuent conduit 32.

During the normal operation of the pebble heater system, valve 34 isopen while valve 39 is closed, thereby permitting free flow of pebblesinto the reaction chamber. When it is desired to measure the pebblecirculation rate of the pebble heater system, pebbles leavingdisengaging chamber 29 are diverted from their usual passage throughpebble conduit 33 and passed into measuring pot 36 by closing valve 34and simultaneously opening valve 39. The pebbles are allowed to flowinto the measuring pot until it is full as observed through the openingin pebble inlet conduit 38 after which vflow of pebbles into the heatingchamber is resumed by closing valve 39 and opening valve 34. Byobserving and recording the time interval required to fill the measuringpot of known volume, the amount of pebbles circulating in the pebbleheater system can be readily determined. During thisoperation, valves 42and 46 in outlet conduits 41 and 44, respectively, are maintained in aclosed position. Upon return to normal operation, the pebbles in thepebble measuring'pot can be passed directly from the pebble measuringpot into the upper portion of the pebble heating chamber through pebbleoutlet 41. Conduit 44 provides .an alternative means for withdrawingpebbles from the pebble measuring pot and can lead to a weighing meanswhereby the weight of the pebbles in the measuring pot can bedetermined. By weighing the amount of pebbles which pass into themeasuring pot during a known interval of time, an alternative method isprovided for measuring the pebble circulation rate. This latter methodof operation also provides a convenient method for calibrating thepebble measuring pot.

When utilizing the apparatus of Figure 2 to measure the pebblecirculation rate, pebbles are diverted from their usual passage throughpebble conduit 33 and passed into pebble measuring pot 36 by closingvalve 34 and simultaneously opening valve 39. Since light sources 51 and53 and their respective photoelectric cells 52 and 54 are ofiset fromthe vertical axis of the measuring pot, the stream of pebbles flowingthereinto does not interrupt the beams of light passing across themeasuring pot. As the pebbles build up in the bottom of the measuringpot, the beam of light between light source 53 and photoelectric cell 54is interrupted, thereby starting the operation of timer-controller 56.As the pebbles continue to fill the measuring pot, the beam of lightpassing between light source 51 and photoelectric cell 52 is alsobroken. The operation of the timer-controller is thereby stopped, givingan indication of the time required to fill the measuring pot withpebbles between the two light sources and photoelectric cells. Oninterruption of the beam of light passing between light source 51 andphotoelectric cell 52, the timer-controller also operates to open valve34 and to close valve 39, thereby permitting the resumption of pebbleflow into the reaction chamber. Since the volume of the portion of themeasuring pot between the two sources of light and photoelectric cellsis a known quantity, the pebble circulation rate can be easilycalculated from the measurement of the time required to fill this volumewith pebbles as indicated by timer-controller 56. It is to be noted thatthe top of the pebble bed in the measuring pot assumes a conical shapeas pebbles are passed into the pot. Since the conical portion of thepebble bed is substantially uniform in height as it moves upwardly inthe measuring pot past the two light sources and photoelectric cells,the time interval as recorded is a correct indication of the timenecessary to fill that volume of the measuring pot between the two lightsources and photoelectric cells. It is also within the contemplation ofthe invention to graduate the scale of the timer-controller so that adirect reading of the pebble circulation rate in thousands of pounds perhour is recorded.

It will be apparent that in accordance with the present invention I haveprovided a simple and positive means and method for determining thecirculation rate of pebbles in a pebble heater apparatus. Accordingly,it is possible at any time during the conduct of a process in the pebbleheater system to determine if the pebble flow rate is being maintainedas required for that particular process. If it is found that the flowrate of pebbles through the pebble heater apparatus is not beingcorrectly maintained, the amount of pebbles entering the pebbleelevating means can be varied by adjusting the pebble feeder in thepebble outlet conduit connecting the lower portion of the reactionchamber with the pebble elevating means. In this manner close controlover the pebble flow rate is possible, and more efiicient operation ofthe pebble heater apparatus is assured.

As will be evident to those skilled in the art, various modifications ofthis invention can be made in the light of the foregoing disclosure anddiscussion without departing from the spirit or scope of the disclosure.

I claim:

1. In a pebble heater system wherein upper and lower closed elongatedshells are disposed substantially in vertical alignment with one anotherand a pebble elevating means has its upper end connected to the upperend portion of said upper shell by a first pebble conduit and its lowerend connected to the lower end portion of said lower shell by a secondpebble conduit, the improvement which comprises a container disposedabove said upper shell; a pebble inlet conduit containing a flow controlmeans and extending from said first pebble conduit to the upper end ofsaid container; a flow control means in said first pebble conduitdownstream, with respect to pebble flow, from the junction of saidpebble inlet conduit and said first pebble conduit; and a pair of outletconduits, each containing flow control means, extending from the lowerportion of said container, one of said outlet conduits being connectedto the upper end of said upper shell.

2. Pebble heater apparatus which comprises, in combination, a firstclosed, upright, elongated shell; pebble inlet means in the upper end ofsaid first shell; gaseous effluent means in the upper end of said firstshell; gaseous material inlet means in-the lower end portion of saidfirst shell; a second closed, upright elongated shell disposed belowsaid first shell; pebble conduit means connecting the lower end portionof said first shell to the upper end portion of said second shell;gaseous effluent outlet means in the upper end portion of said secondshell; gaseous material inlet means in the lower end portion of saidsecond shell; pebble outlet means in the lower end of said second shell;pebble elevating means having its lower end connected to the lower endof said pebble outlet means; a first pebble conduit extending betweenthe.

upper end of said pebble elevating means and said pebble inlet means; acontainer disposed above said first shell; a second pebble conduitcontaining a flow control means and extending from said first pebbleconduit to the upper portion of said container; a flow control means insaid first pebble conduit downstream, with respect to pebble flow, fromthe junction of said first and second pebble conduits; and a pair ofpebble outlets each containing flow control means extending from thelower portion of said container, one of said outlets being connected tothe upper end of said first shell.

3. The pebble heater apparatus of claim 2 in which a first photoelectriccell is positioned in the upper side of said container in line with anoppositely positioned source of light, the imaginary line connectingsaid cell and said light source being ofiset horizontally from thevertical axis of said container; a second photoelectric cell ispositioned in the lower side of said container in line with anoppositely positioned source of light, the imaginary line connectingsaid cell and said light source being ofiset horizontally from thevertical axis of said container; and a timer operatively connected tosaid first and second photoelectric cells.

4. A method for measuring pebble circulation rate in pebble heaterapparatus, said apparatus comprising an upper and a lower chamber, whichcomprises gravitating solid heat exchange material as a uniform,contiguous mass through said upper and lower chambers; removing saidmaterial from the lower portion of said lower chamber; elevating saidmaterial to the upper portion of said upper chamber; diverting the flowof said material from said upper chamber into a pebble measuringchamber; allowing a bed of said material to build up Within saidmeasuring chamber, thereby interrupting a first beam of radiationimpinging upon a first photoelectric cell, said cell thereupon startinga timer to counting time; continuing to allow said bed to build upwithin said measuring chamber, thereby interrupting a second beam ofradiation impinging upon a second photoelectric cell, said cellthereupon stopping said timer from counting time; terminating the flowof said material into said measuring chamber; and allowing said'materialto pass into said upper chamber.

5. An improved method of operating pebble heater apparatus whichcomprises heating a uniform contiguous mass of pebbles contained in apebble heater chamber to a temperature in the range of about 1400 F. to3200 F.; gravitating the heated pebbles from the lower portion of saidpebble heater chamber into the upper portion of a pebble reactionchamber; contacting said heated pebbles with reactant materials;removing efiluent material from the upper portion of said reactionchamber; gravitating cooled pebbles from the lower portion of saidreaction chamber into the lower portion of a pebble elevating means;raising said pebbles to the top of said elevating means; passing saidpebbles from said elevating means into the upper poltion of said pebbleheater chamber; diverting the flow of pebbles from said elevating meansinto a container of known volume for a predetermined period of time,thereby measuring the rate of pebble flow through said pebble heaterapparatus; terminating the flow of pebbles into said container andallowing same to pass into the upper portion of said pebble heaterchamber; passing the pebbles from said container into the upper portionof said pebble heater chamber; and varying the flow of pebbles from saidreaction chamber into the lower portion of said pebble elevating meansin accordance with the measurement of the rate of pebble flow throughthe pebble heater apparatus.

6. The apparatus of claim 1 in which the pebble inlet conduit of saidclosed container is divided into two portions, the upper portion of saidconduit containing said flow control means and the upper end of thelower portion of said conduit beingflared.

References Cited in the file of this patent UNITED STATES PATENTS

1. IN A PEBBLE HEATER SYSTEM WHEREIN UPPER AND LOWER CLOSED ELONGATEDSHELLS ARE DISPOSED SUBSTANTIALLY IN VERTICAL ALIGNMENT WITH ONE ANOTHERAND A PEBBLE ELEVATING MEANS HAS ITS UPPER END CONNECTED TO THE UPPEREND PORTION OF SAID UPPER SHELL BY A FIRST PEBBLE CONDUIT AND ITS LOWEREND CONNECTED TO THE LOWER END PORTION OF SAID LOWER SHELL BY A SECONDPEBBLE CONDUIT, THE IMPROVEMENT WHICH COMPRISES A CONTAINER DISPOSEDABOVE SAID UPPER SHELL; A PEBBLE INLET CONDUIT CONTAINING A FLOW CONTROL